Background and aims

The increasing flooding occurrence associated with climate change, results in soil becoming more vulnerable to heavy metal contamination. However, the mechanisms underlying the combined effects of flooding and metals on the stoichiometry of fast-growing trees (potential for bioremediation) remains poorly understood. Such information is vital to understand how Salix integra Thunb ‘Yizhibi’ (S. integra) alters the nutrient stoichiometry to cope with a single or combined stress of copper (Cu) and flooding.

Methods

S. integra seedlings were cultivated in four soil Cu treatments (control, 50, 150 and 450 mg.kg⁻¹) and examined after a 90-day flooding period. The stoichiometric patterns of C:N:P among different tissues were analyzed upon single or co-exposure to Cu and flooding. Redundancy analysis (RDA) and partial least squares-path modeling (PLS-PM) were used to elucidate the relationship between the C:N:P stoichiometry of soil and plants.

Results

Leaf C concentration negatively correlated with leaf P concentration upon exposure to Cu stress. Flooding significantly increased the leaf C:N and C:P ratios, and leaf N:P increased (3.7–46.3%) with increasing soil Cu dose. The stoichiometric patterns of C:N:P in aboveground tissues were generally affected by flooding, and the ratios of C:N or C:P were in the order of cutting > stem > leaf. The PLS-PM result implied that flooding or Cu had a significantly positive effect on the nutrient stoichiometry (C:N and C:P) of stems and leaves. Moreover, flooding exhibited a stronger effect on C, N and P stoichiometry, with standardized path coefficients of 0.83 and 0.34 in stems and leaves, respectively.

Conclusions

Flooding is a primary factor that alters the C:N:P stoichiometry in tissues of S. integra under Cu induced stress. Flooding is likely to alleviate Cu induced stress via alterations in C:N:P stoichiometry patterns in Salix tissues. Thus, plants can regulate nutrient stoichiometric patterns to cope with single or combined stress, which might be used as an indicator of stress tolerance or ecological adaptation.

中文翻译：

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洪水减轻了对 Salix 的铜胁迫：来自植物组织中化学计量模式的证据

背景和目标

与气候变化相关的洪水发生率不断增加，导致土壤更容易受到重金属污染。然而，洪水和金属对快速生长树木的化学计量（生物修复潜力）的综合影响的机制仍然知之甚少。这些信息对于了解Salix integra Thunb 'Yizhibi' ( S. integra ) 如何改变养分化学计量以应对铜 (Cu) 和洪水的单一或组合压力至关重要。

方法

在四种土壤铜处理（对照，50、150 和 450 mg.kg ^{-1 ）中培养}S. integra幼苗，并在 90 天的淹水期后进行检查。在单次或共同暴露于铜和水浸时分析不同组织中 C:N:P 的化学计量模式。冗余分析 (RDA) 和偏最小二乘路径建模 (PLS-PM) 用于阐明土壤和植物的 C:N:P 化学计量之间的关系。

结果

暴露于铜胁迫时，叶片 C 浓度与叶片 P 浓度呈负相关。洪水显着增加了叶片 C:N 和 C:P 比，叶片 N:P 随着土壤铜剂量的增加而增加（3.7-46.3%）。地上组织中C:N:P的化学计量模式普遍受淹水的影响，C:N或C:P的比例为扦插>茎>叶。PLS-PM 结果表明，淹水或 Cu 对茎和叶的养分化学计量（C:N 和 C:P）具有显着的积极影响。此外，洪水对 C、N 和 P 化学计量的影响更大，茎和叶的标准化路径系数分别为 0.83 和 0.34。

结论

洪水是在铜诱导的压力下改变S. integra组织中 C:N:P 化学计量的主要因素。洪水可能通过改变Salix组织中的 C:N:P 化学计量模式来缓解 Cu 引起的压力。因此，植物可以调节营养化学计量模式以应对单一或复合胁迫，这可用作胁迫耐受性或生态适应的指标。